Circuit Description:
Power for the fan motors is supplied through 2 Maxifuses® in the U/H Electrical Center. The cooling fan relays are energized when current flows from the 2 Maxifuses® through the relay coils to ground through the PCM. The Coolant Fan #1 Relay (Cool Fan 1 Relay) control circuit is grounded for low speed fans operation. The Coolant Fan #1 Relay control circuit and the Coolant Fan #2 Relay control circuit (Cool Fan Relay and Cool Fan 2 Relay) are grounded for high speed fans operation.
During low speed fans operation the PCM supplies a ground path for Cool Fan 1 Relay. This closes the Cool Fan 1 Relay contacts, allowing current to flow from the U/H Electrical Center through the relay contacts to the left engine cooling fan. During low speed operation, the ground path for the primary cooling fan is through the engine Cool Fan Relay and the right engine cooling fan motor. The result is a series circuit with both cooling fans running at low speed.
During high speed cooling fan operation the PCM supplies a ground path for the Cool Fan 1 Relay. The PCM also supplies a ground path for Cool Fan Relay and Cool Fan 2 Relay. This closes all three cooling fan relays. During high speed fans operation, both the right and the left engine cooling fans are supplied current from the U/H Electrical Center and each cooling fan has its own ground path.
Diagnostic Aids
Check for the following conditions:
| • | Poor connection at the PCM, cooling fan relays, or cooling fan motors. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. |
| • | Damaged harness. Inspect the wiring harness for damage. |
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
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Stored diagnostic trouble codes may affect engine cooling fans operation. This diagnostic table may lead to improper diagnosis and replacement of good parts if diagnostic trouble codes are present.
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Ambient temperature must be above 9°C (48°F) before the PCM will enable the cooling fans due to A/C request. The PCM will enable the cooling fans if A/C refrigerant pressure increases regardless of ambient temperature.
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This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming
Step | Action | Value(s) | Yes | No | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On Board Diagnostic (OBD) System Check performed? | -- | ||||||||||||
Are any PCM DTC(s) stored? | -- | Diagnose the PCM DTC(s) first. Go to Powertrain Control Module Diagnosis | ||||||||||||
3 |
Are the cooling fan(s) running? | -- | ||||||||||||
4 |
Are both cooling fans running at low speed? | -- | ||||||||||||
5 |
Are both fans running at high speed? | -- | ||||||||||||
|
Important: : Ambient temperature must be above 9°C (48°F).
Are the cooling fans on ? | -- | Go to Diagnostic Aids | ||||||||||||
7 | View A/C Request on the scan tool. Does A/C Request on the scan tool display Yes? | -- | Go to Powertrain Control Module Controlled Air Conditioning (A/C) Circuit Diagnosis | |||||||||||
8 | Is either cooling fan running? | -- | ||||||||||||
9 | Is the left cooling fan running? | -- | ||||||||||||
10 |
Is the left engine cooling fan running? | -- | ||||||||||||
11 | Remove the Cool Fan relay from the Underhood Electrical Center. Is the left engine cooling fan running? | -- | ||||||||||||
12 | Locate and repair short to voltage in CKT 409. Refer to Repair Procedures in Electrical Diagnosis. Is the action complete? | -- | -- | |||||||||||
13 |
Was a problem found? | -- | ||||||||||||
14 |
Is the right engine cooling fan running? | -- | ||||||||||||
15 | Locate and repair short to battery positive voltage in circuit 532 and 409. If a problem is found repair as necessary. Refer to Repair Procedures in Electrical Diagnosis. Was a problem found? | -- | ||||||||||||
16 |
Is the test light on ? | -- | ||||||||||||
17 |
Is action complete? | -- | -- | |||||||||||
18 | Probe Cool Fan 1 relay cavity 86 with a test light connected to ground. Is the test light on ? | -- | ||||||||||||
19 |
Is action complete? | -- | -- | |||||||||||
20 |
Is the test light on? | -- | ||||||||||||
21 |
Is the test light on ? | -- | ||||||||||||
22 |
Are both cooling fans running? | -- | ||||||||||||
23 |
Was a problem found? | -- | ||||||||||||
24 |
Was a problem found? | -- | ||||||||||||
25 |
Is the test light on? | -- | ||||||||||||
26 | Locate and repair open in the Coolant Fan 1 relay control circuit between the PCM and Cool Fan 1 relay cavity 85. Is the action complete? | -- | -- | |||||||||||
27 |
Is the test light on? | -- | ||||||||||||
28 | Connect a test light between Cool Fan relay in Underhood Electrical Center cavities 30 and 87A. Is the test light on? | -- | ||||||||||||
29 |
Was a problem found? | -- | ||||||||||||
30 |
Was a problem found? | -- | ||||||||||||
31 |
Was a problem found? | -- | ||||||||||||
32 | Using scan tool, view A/C Request. Does the scan tool display Yes? | -- | Go to Powertrain Control Module Controlled Air Conditioning (A/C) Circuit Diagnosis | |||||||||||
33 | Are both cooling fan(s) running at low speed? | -- | ||||||||||||
34 | Remove Cool Fan 1 relay from the Underhood Electrical Center. Are the cooling fans running? | -- | ||||||||||||
35 | Locate and repair short to voltage in CKT 409 and 504. Refer to Repair Procedures in Electrical Diagnosis. Is the action complete? | -- | -- | |||||||||||
36 | Using a test light connected to battery positive voltage, probe Cool Fan 1 relay cavity 86. Is the test light on? | -- | ||||||||||||
37 | Replace Cool Fan 1 relay. Is the action complete? | -- | -- | |||||||||||
38 |
Is the test light on? | -- | ||||||||||||
39 | Locate and repair short to ground in the Cool Fan 1 relay control circuit. Refer to Repair Procedures in Electrical Diagnosis. Is the action complete? | -- | -- | |||||||||||
40 | Are both cooling fans running at high speed? | -- | ||||||||||||
41 | View A/C Pressure on the scan tool. Does the scan tool display voltage less than the specified value? | 1.2 V | ||||||||||||
42 |
Is the right engine cooling fan running at high speed? | -- | ||||||||||||
43 |
Was a problem found? | -- | ||||||||||||
44 |
Does the scan tool display voltage near the specified value? | 0.0 V | ||||||||||||
45 | Probe the A/C refrigerant pressure signal circuit with a Digital Multimeter J 39200 connected to the A/C refrigerant pressure sensor ground. Does the digital multimeter display voltage near the specified value? | 0.0 V | ||||||||||||
46 | Probe the A/C refrigerant pressure sensor ground with a test light to battery positive voltage. Is the test light on? | -- | ||||||||||||
47 | Probe the A/C refrigerant pressure sensor 5 Volt Reference circuit with a Digital Multimeter J 39200 connected to the A/C refrigerant pressure sensor ground. Does the digital multimeter display voltage near the specified value? | 5.0 V | ||||||||||||
48 | Replace the A/C refrigerant pressure sensor. Refer to On-Vehicle Service in Heater, Ventilation, and Air Conditioning. Is the action complete? | -- | -- | |||||||||||
49 | Locate and repair open or short to voltage in the A/C refrigerant pressure sensor ground circuit. Refer to Repair Procedures in Electrical Diagnosis. Is the action complete? | -- | -- | |||||||||||
50 | Locate and repair open or short to ground in the A/C refrigerant pressure sensor 5 Volt Reference circuit. Refer to Repair Procedures in Electrical Diagnosis. Is the action complete? | -- | -- | |||||||||||
51 | Locate and repair short to voltage in the A/C refrigerant pressure signal circuit. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |||||||||||
52 |
Is the left engine cooling fan running at high speed? | -- | ||||||||||||
53 | Remove the Cool Fan 2 relay from the Underhood Electrical Center. Is the left engine cooling fan running at high speed? | -- | ||||||||||||
54 | Locate and repair short to battery positive voltage in CKT 504. Refer to Repair Procedures in Electrical Diagnosis. Is the action complete? | -- | -- | |||||||||||
55 | Locate and repair short to battery positive voltage in CKT 504. Refer to Repair Procedures in Electrical Diagnosis. If a problem is found repair as necessary. Was a problem found? | -- | ||||||||||||
56 |
Was a problem found? | -- | ||||||||||||
57 |
Was a problem found? | -- | ||||||||||||
58 |
Is the test light on? | -- | ||||||||||||
59 |
Is the test light on? | -- | ||||||||||||
60 |
Was a problem found? | -- | ||||||||||||
61 |
Is the test light on? | -- | ||||||||||||
62 | Probe terminal A at the left engine cooling fan connector with a test light to battery positive voltage. Is the test light on? | -- | ||||||||||||
63 |
Is the action complete? | -- | -- | |||||||||||
64 |
Is the test light on? | -- | ||||||||||||
65 | Locate and repair open in the battery positive voltage circuit to high speed engine Cool Fan relay. Refer to Repair Procedures in Electrical Diagnosis. Is the action complete? | -- | -- | |||||||||||
66 | Probe Cool Fan relay cavity 30 with a test light connected to ground. Is the test light on? | -- | ||||||||||||
67 | Locate and repair open in battery positive voltage circuit to Cool Fan relay cavity 30. Refer to Repair Procedures in Electrical Diagnosis. Is the action complete? | -- | -- | |||||||||||
68 |
Was a problem found? | -- | ||||||||||||
69 |
Was a problem found? | -- | ||||||||||||
70 | Replace Cool Fan relay. Is the action complete? | -- | -- | |||||||||||
71 |
Is the test light on? | -- | ||||||||||||
72 | Locate and repair open in battery positive voltage circuit to Cool Fan 2 relay cavity 85. Refer to Repair Procedures in Electrical Diagnosis. Is the action complete? | -- | -- | |||||||||||
73 | Probe Cool Fan 2 relay cavity 87 in the Underhood Electrical Center with a test light to battery positive voltage. Is the test light on? | -- | ||||||||||||
74 | Locate and repair open in circuit between Cool Fan 2 relay cavity 87 and Cool Fan relay cavity 87a in the Underhood Electrical Center and ground. Refer to Repair Procedures in Electrical Diagnosis. Is the action complete? | -- | -- | |||||||||||
75 |
Was a problem found? | -- | ||||||||||||
76 | Replace the Cool Fan 2 relay in the Underhood Electrical Center. Is the action complete? | -- | -- | |||||||||||
Replace the PCM. Important: : The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | ||||||||||||
78 | Repair open in the Cool Fan relay cavity 86 and Cool Fan 2 relay cavity 86 control circuit to PCM. Refer to Repair Procedures in Electrical Diagnosis. Is the action complete? | -- | -- | |||||||||||
79 | Replace the left engine cooling fan motor. Refer to On-Vehicle Service in Cooling and Radiator. Is the action complete? | -- | -- | |||||||||||
80 | Replace the right engine cooling fan motor. Refer to On-Vehicle Service in Cooling and Radiator. Is the action complete? | |||||||||||||
81 |
Observe the cooling fans. Are the cooling fans running? | -- | ||||||||||||
82 |
Are both cooling fans running at low speed? | -- | ||||||||||||
83 |
Are both cooling fans running at high speed? | -- | System OK |
